Wireless device using an array of ground plane boosters for multiband operation

ABSTRACT

A radiating system comprises a radiating structure including two or more radiation boosters for transmission and reception of electromagnetic wave signals, a radiofrequency system and an external port. The radiating system is capable of operation in at least a first and second frequency regions which are preferably separated. The radiofrequency system comprises two or more matching networks and a combining structure at which, in transmission, electromagnetic wave signals from the external port are substantially separated and coupled to each radiation booster based on the frequency of the signals; and, in reception, signals from each radiation booster are combined and coupled to the external port. The radiofrequency system provides impedance matching to the radiating structure in the first and second frequency regions at the external port. An advantage of such radiating system is that signals from the first and second frequency regions are fed to and retrieved in one single port.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119(e) from U.S.Provisional Patent Application Ser. No. 62/139,809, filed Mar. 30, 2015,and claims priority under 35 U.S.C. §119 to Application No. EP15161245.4 filed on Mar. 27, 2015, the entire contents of which arehereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to the field of wireless handheld devices,and generally to wireless portable devices which require thetransmission and reception of electromagnetic wave signals.

BACKGROUND

Wireless electronic devices typically handle one or more cellularcommunication standards, and/or wireless connectivity standards, and/orbroadcast standards, each standard being allocated in one or morefrequency bands, and said frequency bands being contained within one ormore regions of the electromagnetic spectrum.

For that purpose, a typical wireless electronic device must include aradiating system capable of operating in one or more frequency regionswith an acceptable radioelectric performance (in terms of, for instance,reflection coefficient, standing wave ratio, impedance bandwidth, gain,efficiency, or radiation pattern). The integration of the radiatingsystem within the wireless electronic device must be effective to ensurethat the overall device attains good radio-electric performance (such asfor example in terms of radiated power, received power, sensitivity)without being disrupted by electronic components and/or human loading.

The space within the wireless electronic device is usually limited andthe radiating system has to be included in the available space. Theradiating system is expected to be small to occupy as little space aspossible within the device, which then allows devices to be smaller, orfor the addition of more specific components and functionalities intothe device. It is even more critical in the case in which the wirelessdevice is a multifunctional wireless device, such as the ones describedin commonly-owned patent applications US2014/0253395 and WO2008/009391.The entire disclosures of patent applications US2014/0253395 andWO2008/009391 are hereby incorporated by reference.

Besides radiofrequency performance, small size and reduced interactionwith human body and nearby electronic components, one of the currentlimitations of the prior-art is that generally the antenna system iscustomized for every particular wireless handheld device model. Themechanical architecture of each device is different and the volumeavailable for the antenna severely depends on the form factor of thewireless device model together with the arrangement of the multiplecomponents embedded into the device (e.g., displays, keyboards, battery,connectors, cameras, flashes, speakers, chipsets, memory devices, etc.).As a result, the antenna within the device is mostly designed ad hoc forevery model, resulting in a higher cost and a delayed time to market. Inturn, as typically the design and integration of an antenna element fora radiating structure is customized for each wireless device, differentform factors or platforms, or a different distribution of the functionalblocks of the device will force to redesign the antenna element and itsintegration inside the device almost from scratch.

A radiating system for a wireless handheld or portable device typicallyincludes a radiating structure comprising an antenna element whichoperates in combination with a ground plane layer providing a determinedradiofrequency performance in one or more frequency regions of theelectromagnetic spectrum. Typically, the antenna element has a dimensionclose to an integer multiple of a quarter of the wavelength at afrequency of operation of the radiating structure, so that the antennaelement is at resonance or substantially close to resonance at thefrequency of operation, and a radiation mode is excited on the antennaelement. Due to given space limitations in the device and the necessityof providing operation in two or more frequency bands that, in somecases, are located in at least two separate frequency regions of theelectromagnetic spectrum, the antenna elements usually present complexmechanical designs and considerable dimensions, mainly due to the factthat antenna performance is highly related to the electrical dimensionsof the antenna element. Although the radiating structure is usually veryefficient at the resonant frequency of the antenna element and maintainsa similar performance within a frequency range defined around saidresonant frequency (or resonant frequencies), outside said frequencyrange the efficiency and other relevant antenna parameters deterioratewith an increasing distance to said resonant frequency.

Some techniques for miniaturizing and/or optimizing the multibandbehavior of an antenna element have been described in the prior-art.However, the radiating structures described therein still rely onexciting a radiation mode on the antenna element for each one of thefrequency bands of operation.

In this sense, a radiating system such as the one described in thepresent invention not requiring a complex and/or large antenna formed bymultiple arms, slots, apertures and/or openings and a complex mechanicaldesign is preferable in order to minimize such undesired externaleffects and simplify the integration within the wireless device.

Some other attempts have focused on antenna elements not requiring acomplex geometry while still providing some degree of miniaturization byusing an antenna element not resonant in the one or more frequencyranges of operation of the wireless device.

For example, commonly-owned patent application WO2007/128340 discloses awireless portable device comprising a non-resonant antenna element forreceiving broadcast signals (such as, for instance, DVB-H, DMB, T-DMB orFM). The wireless portable device further comprises a ground plane layerthat is used in combination with said antenna element. Although theantenna element has a first resonant frequency above the frequency rangeof operation of the wireless device, the antenna element is still themain responsible for the radiation process and for the radio-frequencyperformance of the wireless device. No radiation mode can besubstantially excited on the ground plane layer because the ground planelayer is electrically short at the frequencies of operation (i.e., itsdimensions are much smaller than the wavelength). For this kind ofnon-resonant antenna elements, a matching circuitry is added formatching the antenna to a level of SWR in a limited frequency range,which in this particular case can be around SWR≦6.

Commonly-owned patent application WO2008/119699 describes a wirelesshandheld or portable device comprising a radiating system capable ofoperating in two frequency regions. The radiating system comprises anantenna element having a resonant frequency outside said two frequencyregions, and a ground plane layer. In this wireless device, while theground plane layer contributes to enhance the electromagneticperformance of the radiating system in the two frequency regions ofoperation, it is still necessary to excite a radiation mode on theantenna element. In fact, the radiating system relies on therelationship between a resonant frequency of the antenna element and aresonant frequency of the ground plane layer for the radiating system tooperate properly in said two frequency regions. Nevertheless, thesolution still relies on an antenna element whose size is related to aresonant frequency that is outside of the two frequency regions.

In order to reduce the volume occupied in the wireless handheld orportable device as much as possible, recent trends in handset antennadesign are oriented to maximize the contribution of the ground plane tothe radiation process by using small non-resonant elements. However,non-resonant elements may require of complex radiofrequency systems.Thus, the challenge of these techniques mainly relies on said complexity(combination of inductors, capacitors, and transmission lines), which isrequired to satisfy impedance bandwidth and efficiency specifications.

Patent applications WO2010/015365 and WO2010/015364 are intended forsolving some of the aforementioned drawbacks. Namely, they describe awireless handheld or portable device comprising a radiating systemincluding a radiating structure and a radiofrequency system. Theradiating structure is formed by a ground plane layer presentingsuitable dimensions as for supporting at least one efficient radiationmode and at least one radiation booster capable of couplingelectromagnetic energy to said ground plane layer. The radiation boosteris not resonant in any of the frequency regions of operation and,consequently, a radiofrequency system is used to properly match theradiating structure to the desired frequency bands of operation. Morespecifically, in WO2010/015364 each radiation booster is intended forproviding operation in a particular frequency region. Thus, theradiofrequency system is designed in such a way that the first internalport associated to a first radiation booster is highly isolated from thesecond internal port associated to a second radiation booster. Saidradiofrequency system usually comprises a matching network includingresonators for each one of the frequency regions of operation and a setof filters for each one of the frequency regions of operation. Thus,said radiofrequency system requires multiple stages and the performanceof the radiating systems in terms of efficiency may be affected by theadditional losses of the components.

Patent applications WO2014/012796 and US2014/0015730 disclose aconcentrated wireless device comprising a radiating system including aradiating structure and a radiofrequency system, such device operatestwo or more frequency regions of the electromagnetic spectrum. A featureof said radiating system is that the operation in at least two frequencyregions is achieved by one radiation booster, or by at least tworadiation boosters, or by at least one radiation booster and at leastone antenna element, wherein the radiofrequency system modifies theimpedance of the radiating structure, providing impedance matching tothe radiating system in the at least two frequency regions of operationof the radiating system.

In patent application US2013/0342416 there is disclosed a radiatingsystem that transmits and receives in first and second frequency regionsand includes a radiating structure comprising radiation boosters, or aradiation booster and a radiating element, or radiating elements. Theradiating system further includes a radiofrequency system including:first and second reactance cancellation elements providing impedanceshaving an imaginary part close to zero for respective frequencies in thefirst and second frequency regions, and a delay element interconnectingthe first and second reactance cancellation elements to provide adifference in phase to produce first and second impedance loops in thefirst and second frequency regions, respectively, at an external port.The difference in phase provides operation in at least two frequencybands, each one allocated in a different frequency region of theelectromagnetic spectrum, and/or increases the number of operatingfrequency bands in at least one frequency region of the electromagneticspectrum, and/or increases the number of operating frequency bands in atleast two frequency regions of the electromagnetic spectrum.

Patent applications WO2014/012842 and US2014/0015728 disclose verycompact, small size and light weight radiation boosters operating insingle or in multiple frequency bands. Such radiation boosters areconfigured to be used in radiating systems that may be embedded into awireless handheld device. Said patent applications further discloseradiation booster structures and their manufacturing methods that enablereducing the cost of both the booster and the entire wireless deviceembedding said booster inside the device. The entire disclosure ofaforesaid application numbers WO2014/012842 and US2014/0015728 arehereby incorporated by reference.

Patent applications U.S. Ser. No. 62/028,494 and EP14178369 disclose awireless device including at least one slim radiating system having aslim radiating structure and a radio-frequency system. The slimradiating structure includes one or more booster bars. The booster baris characterized by its slim width and height factors which facilitateits integration within the wireless device and the excitation of aresonant mode in the ground plane layer, and by its location factor thatenables to achieve the most favorable radio-frequency performance forthe available space to allocate the booster bar. The entire disclosureof aforesaid application numbers U.S. Ser. No. 62/028,494 and EP14178369are hereby incorporated by reference.

Another technique, as disclosed in U.S. Pat. No. 7,274,340, is based onthe use of two coupling elements. According to the invention, quad-bandoperation (GSM 1800/1900 and GSM850/900 bands) is provided with twocoupling elements: a low-band (LB) coupling element (for the GSM850/900bands), and a high-band (HB) coupling element (for the GSM1800/1900bands), where the impedance matching is provided through the addition oftwo matching circuits, one for the LB coupling element and another onefor the HB coupling element. In spite of using non-resonant elements,the size of the element for the low band is significantly large, being1/9.3 times the free-space wavelength of the lowest frequency for thelow frequency band. Due to such size, the low band element would be aresonant element at the high band. Additionally, the operation of thissolution is closely linked to the alignment of the maximum E-fieldintensity of the ground plane and the coupling element. The size of thelow band element undesirably contributes to increase the printed circuitboard (PCB) space required by the antenna module.

Therefore, a wireless device not requiring an antenna element yetproviding suitable radio-frequency performance to operate in a widerange of communication bands within multiple regions of theelectromagnetic spectrum would be advantageous as it would ease theintegration of the radiating structure into the wireless handheld orportable device. The volume freed up by the absence of a large andcomplex antenna element would enable smaller and/or thinner devices, asslim electronic devices, or even to adopt radically new form factorswhich are not feasible today due to the presence of an antenna elementfeatured by a considerable volume.

SUMMARY

It is an object of the present invention to provide a wirelesselectronic device (such as for instance but not limited to a mobilephone, a smartphone, a phablet, a tablet, a PDA, an MP3 player, aheadset, a USB dongle, a GPS system, a laptop computer, a gaming device,a digital camera, a wearable device as a smart watch, a PCMCIA, Cardbus32 card, a sensor, or generally a multifunction wireless device whichcombines the functionality of multiple devices) comprising a radiatingsystem that covers a wide range of radio frequencies and handlesmultiple communication bands while exhibiting a suitable radio frequencyperformance.

Another object of the present invention is to provide a radiating systemsuitable for being included within electronic devices. Such radiatingsystem advantageously comprises a radiating structure including two ormore radiation boosters for the transmission and reception ofelectromagnetic wave signals, a radiofrequency system and an externalport. Such radiating system is capable of operation in at least a firstfrequency region and a second frequency region of the electromagneticspectrum; said at least first and second frequency regions arepreferably separated so that the lowest frequency of the secondfrequency region is above (i.e., at a frequency higher than) the highestfrequency of the first frequency region. The radiofrequency systemcomprises two or more matching networks and a combining structure atwhich, in transmission, electromagnetic wave signals from the externalport are substantially separated and coupled to each radiation boosterbased on the frequency of the signals; and, in reception, signals fromeach radiation booster are combined and coupled to the external port.The radiofrequency system provides impedance matching to the radiatingstructure in said first and second frequency regions of theelectromagnetic spectrum at the external port. An associated advantageof such radiating system is that signals from the first and secondfrequency regions are fed to (i.e., in transmission) and retrieved(i.e., in reception) in one single port (i.e., the external port).

It is also an object of the present invention to provide aradiofrequency system that comprises transmission lines particularlyconvenient for interconnecting one or more radiation boosters withradiofrequency front-end modules or chips when the radiation boostersare located substantially proximate to the edges of a printed circuitboard. In radiating structures including two or more radiation boosters,each one of the radiation boosters may be substantially in charge of thetransmission and/reception of electromagnetic wave signals of oneparticular frequency region, and such transmission lines together withother components of the matching networks may be advantageouslyconfigured to present, at the combining structure, an impedancerelatively close to the reference impedance (generally between 12Ω and200Ω when the reference impedance is 50Ω at the port coupled to theradiation booster operating signals from said frequency region, andfurther configured to present a high impedance at the port/s of theother radiation booster/s (generally above 200Ω, such as 300Ω, 400Ω,500Ω or even higher than 500Ω). This is especially advantageous forsimplifying the radiofrequency system as the matching networks requirefewer components for providing impedance matching in the two or morefrequency regions of operation.

Although the present invention refers to radiating systems comprisingradiation boosters, antenna systems comprising one or more radiatingelements may also take advantage of such transmission lines,particularly in those cases in which at least one radiating element issubstantially close to the edges of the electronic device. This isgenerally so due to the fact that there is a reduced amount of freespace in the printed circuit boards where circuitry and components ofthe device are installed, and thus connection between the radiatingelements and the RF front-end modules is not simple. This may be solvedwith the transmission lines disclosed in the present invention.

An advantageous aspect of the present invention is that the lengths ofthe transmission lines may be adjusted while the radiofrequency systemstill provides said substantial filtering behavior in the signal pathsthat couple the radiation boosters to the combining structure. In priorart solutions configured to operate in at least two frequency regionsand in which delay elements are included for generating a difference inphase, adjusting the length (e.g., the delay) of said delay elementsrequires taking into consideration the impedances of the two or moreradiation boosters or radiating elements. In contrast, in the presentinvention, adjusting the length of one transmission line mainly dependson the total impedance of the respective radiation booster and thematching network associated to said radiation booster, thus eachradiation booster being more independent from the others.

An aspect of the present invention relates to the use of the groundplane layer of the radiating system as a main source of radiation. Theradiation boosters of a radiating system advantageously couple theelectromagnetic energy from the radiofrequency system to the groundplane layer in transmission, and from the ground plane layer to theradiofrequency system in reception. Said radiation boosters excite aradiation mode in the ground plane layer enabling the radiation from theground plane layer.

The radiation boosters, as shown herein, are configured to be used inradiating systems according to the present invention and may be any ofthe radiation boosters disclosed in patent applications US2014/0015728and WO2014/012842, or booster bars disclosed in patent applications U.S.Ser. No. 62/028,494 and EP14178369. A radiating structure from thepresent invention comprises radiation boosters that fit in an imaginarysphere having a diameter smaller than ⅓ of a radiansphere correspondingto the lowest frequency of the first frequency region of the radiatingsystem. In some cases, the radiation boosters also fit in an imaginarysphere having a diameter smaller than ¼, or preferably smaller than ⅙,or even more preferably smaller than 1/10 of a radianspherecorresponding to said frequency. The radiansphere is defined as animaginary sphere having a radius equal to the operating wavelengthdivided by two times π (pi). In some embodiments, the radiation boostermay have a maximum size at least smaller than 1/15 of the free-spacewavelength corresponding to the lowest frequency of the first frequencyregion of the radiating system. In some embodiments, the maximum size ofa radiation booster is at least smaller than 1/20, and/or 1/30, and/or1/50, and/or 1/100 of the free-space wavelength corresponding to thelowest frequency of the first frequency region of operation. In some ofthese examples, the radiation booster has a maximum size larger than1/1400, 1/700, 1/350, 1/250, 1/180, 1/140, or 1/120 times the free-spacewavelength corresponding to the lowest frequency of the first frequencyregion of the radiating system. Thus in some examples, a radiationbooster has a maximum size advantageously smaller than a first fractionof the free-space wavelength corresponding to the lowest frequency ofthe first frequency region but larger than a second fraction of saidfree-space wavelength.

Accordingly, the maximum size of a radiation booster is defined by thelargest dimension of a booster box that completely encloses saidradiation booster, and in which the radiation booster is inscribed. Morespecifically, a booster box for a radiation booster is defined as beingthe minimum-sized parallelepiped of square or rectangular faces thatcompletely encloses the radiation booster and wherein each one of thefaces of said minimum-sized parallelepiped is tangent to at least apoint of said radiation booster. Moreover, each possible pair of facesof said minimum-size parallelepiped sharing an edge forms an inner angleof 90°. For each of the radiation boosters included in a radiatingstructure a different booster box is defined. In some examples, one ofthe dimensions of a booster box can be substantially smaller than any ofthe other two dimensions, or even be close to zero. In such cases, saidbooster box collapses to a practically two-dimensional entity. The termdimension refers to an edge between two faces of said parallelepiped.

In some preferred examples, the area defined by the two largestdimensions of a booster box is advantageously small compared to thesquare of the wavelength corresponding to the lowest frequency of thefirst frequency region; in particular, a ratio between said area and thesquare of the wavelength corresponding to the lowest frequency of thefirst frequency region may be advantageously smaller than at least oneof the following percentages: 0.15%, 0.12%, 0.10%, 0.08%, 0.06%, 0.04%,or even 0.02%. In some of these examples, a ratio between the areadefined by the two largest dimensions of a booster box and the square ofthe wavelength corresponding to the lowest frequency of the secondfrequency region may also be advantageously smaller than at least one ofthe following percentages: 0.50%, 0.45%, 0.40%, 0.35%, 0.30%, 0.25%,0.20%, 0.15%, 0.10%, or even 0.05%.

Moreover, in some embodiments according to the present invention, eachone of the radiation boosters entirely fits inside a limiting volumeequal or smaller than L³/25000, and in some cases smaller than L³/50000,and/or L³/100000, and/or L³/150000, and/or L³/200000, and/or L³/300000,and/or L³/400000, and/or even smaller than L³/500000, being L thewavelength corresponding to the lowest frequency of the first frequencyregion.

The radiation boosters may include one or more booster elements. Eachbooster element may include a dielectric material, and in someembodiments, a single standard layer of dielectric material spacing twoor more conductive elements of the booster element. A booster elementmay be formed by printing or depositing conductive material in a firstsurface and a second surface of the dielectric material (for instance,two opposed sides such as the top and the bottom ones) and addingseveral vias to electrically connect the conductive material in thefirst surface with the conductive material in the second surface. Insome preferred examples, the conductive material in each of the firstand second surface of a booster element has a substantially polygonalshape. Some possible polygonal shapes are, for instance but not limitedto, squares, rectangles, and trapezoids. In some embodiments in which aradiation booster includes a plurality of booster elements, said boosterelements are electrically connected one to each other.

Each radiation booster may be separated from the ground plane layer by agap. In the context of this document, the gap characterizing a radiationbooster refers to a minimum distance between a point at an edge of theground plane layer and a point at an edge of the bottom conductivesurface of the radiation booster. The location of the radiation boosteris characterized by a location factor that is a ratio between the widthof the radiation booster and said gap. In a preferred example in whichthe radiation boosters are located beyond an edge of the ground planelayer, the location factor is between 0.3 and 3.5.

In a preferred example, a radiating structure is arranged within awireless handheld or portable device in such a manner that the radiationboosters are attached to (e.g., soldered to or attached by other meansas known in the art) conductive elements or traces on a printed circuitboard. In said preferred example, there is no ground plane in theorthogonal projections of the radiation boosters onto the planecontaining the ground plane layer which, for example, may be formed in alayer of the printed circuit board. In other words, the orthogonalprojections of said radiation boosters onto said plane has no areaoverlapping the ground plane layer. In some other cases, there may be atleast partial overlapping between the orthogonal projection of one ormore radiation boosters and the ground plane layer.

In some embodiments, a radiating structure may comprise more than oneground plane layer, like for instance two, three or even more groundplane layers or conductive materials acting as the ground plane for theradiating structure. In such embodiments, some or all ground planelayers may be electrically interconnected one to each other.

A preferred embodiment of the present invention relates to a wirelesshandheld or portable device comprising a radiating system configured tooperate electromagnetic wave signals from a first frequency region and asecond frequency region, wherein the lowest frequency of the secondfrequency region is above the highest frequency of the first frequencyregion. The radiating system comprises a radiating structure, aradiofrequency system and an external port. The radiating structurecomprises: a printed circuit board including a ground plane layer; afirst radiation booster connected to a first feeding line, a secondradiation booster connected to a second feeding line, wherein each ofthe first and second radiation boosters fits in an imaginary spherehaving a diameter smaller than ⅓ of a radiansphere having a radius equalto a free-space wavelength corresponding to the lowest frequency of thefirst frequency region, divided by two times π (pi); a first internalport defined between a connection point of the first radiation boosterand a first connection point of the ground plane layer, and a secondinternal port defined between a connection point of the second radiationbooster and a second connection point of the ground plane layer. Theradiofrequency system comprises: a combining structure; a first matchingnetwork; a second matching network; and a third matching network. Thefirst matching network is connected to the first feeding line and thecombining structure, the first matching network comprising at least afirst transmission line. The second matching network is connected to thesecond feeding line and the combining structure, the second matchingnetwork comprising at least a second transmission line. The thirdmatching network is connected to the combining structure and to theexternal port.

In said preferred embodiment, the input impedance of the radiatingstructure at the first internal port, when disconnected from theradiofrequency system, has an imaginary part not equal to zero for anyfrequency of the first frequency region; the input impedance of theradiating structure at the second internal port, when disconnected fromthe radiofrequency system, has an imaginary part not equal to zero forany frequency of the first frequency region. The radiofrequency systemmodifies the impedance of the radiating structure to provide impedancematching to the radiating system within the first and second frequencyregions at the external port.

In some cases, the input impedance of the radiating structure at thefirst internal port, when disconnected from the radiofrequency system,has an imaginary part not equal to zero for any frequency of the firstand second frequency regions; and the input impedance of the radiatingstructure at the second internal port, when disconnected from theradiofrequency system, has an imaginary part not equal to zero for anyfrequency of the first and second frequency regions.

Each of the at least first and second transmission lines in the firstand second matching networks, respectively, is characterized by one edgebeing substantially close to the ground plane layer. Each of the atleast first and second transmission lines is characterized by a width atleast 2.5 times greater than a gap separating each of the at least firstand second transmission lines and the ground plane layer.

A radiating system according to the present invention may be configuredto transmit and receive signals in frequency bands like for example, butnot limited to: LTE700 (698-798 MHz), LTE800 (791-862 MHz), GSM850(824-894 MHz), GSM900 (880-960 MHz), GSM1800 (1710-1880 MHz), GSM1900(1850-1990 MHz), WCDMA2100 (1920-2170 MHz), CDMA1700 (1710-2155 MHz),LTE2300 (2300-2400 MHz), LTE2600 (2500-2690 MHz), LTE3500 (3.4-3.6 GHz),LTE3700 (3.6-3.8 GHz), WiFi (2.4-2.5 GHz and/or 4.9-5.9 GHz), etc. Suchradiating systems may operate five, six, seven, eight, nine, ten or evenmore frequency bands.

In the context of this document, a frequency band preferably refers to arange of frequencies used by a particular cellular communicationstandard, a wireless connectivity standard or a broadcast standard;while a frequency region preferably refers to a continuum of frequenciesof the electromagnetic spectrum. For example, the GSM1800 standard isallocated in a frequency band from 1710 MHz to 1880 MHz while theGSM1900 standard is allocated in a frequency band from 1850 MHz to 1990MHz. A wireless device operating the GSM1800 and the GSM1900 standardsmust have a radiating system capable of operating in a frequency regionfrom 1710 MHz to 1990 MHz. As another example, a wireless deviceoperating the GSM850 standard (allocated in a frequency band from 824MHz to 894 MHz) and the GSM1800 standard must have a radiating systemcapable of operating in two separate frequency regions.

In some embodiments, a ratio between the lowest frequency of the secondfrequency region and the lowest frequency of the first frequency regionis greater than 1.5. In some other embodiments, said ratio may begreater than 1.8, or 2.0, or 2.2, or even greater than 2.4. In some ofthese embodiments, a ratio between the lowest frequency of the secondfrequency and the highest frequency of the first frequency region may begreater than 1.2, or 1.5, or 1.8, or 2.0, or 2.2, or even greater than2.4.

Moreover, a radiating system according to the present invention mayadvantageously feature an impedance bandwidth in the first frequencyregion larger than 5%, or 10%, or 15%, or even larger than 20%. Inaddition, such radiating system may also feature an impedance bandwidthin the second frequency region larger than 5%, or 10%, or 15%, or 20%,or 25%, or 30%, or 35%, or even larger than 40%. The impedance bandwidthis defined as the difference between the highest and lowest frequenciesof a frequency region, divided by the central frequency of thatfrequency region.

A radiating structure according to the present invention, whendisconnected from the radiofrequency system, may feature at one, some orall of the internal ports a first resonant frequency at a frequencyhigher than the highest frequency of the first frequency region. Theinput impedance of the radiating structure measured at said internalport/s (in absence of a radiofrequency system connected to it) may havean important reactance within the frequencies of said first frequencyregion. In this case, a ratio between said first resonant frequency ofthe radiating structure measured at said internal port/s (whendisconnected from the radiofrequency system) and the highest frequencyof the first frequency region is advantageously greater than 1.2. Insome cases, said ratio may be even greater than 1.5, 1.8, 2.0, 2.2, 2.4,2.6, 2.8, or 3.0. In some examples, a ratio between said first resonantfrequency of the radiating structure measured at said internal port/s(in absence of a radiofrequency system connected to it) and the lowestfrequency of the first frequency region is advantageously greater than1.3, or even greater than 1.4, 1.5, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8, or3.0.

In some embodiments, the first resonant frequency of the radiatingstructure, measured at its internal port when disconnected from theradiofrequency system, is above the highest frequency of the secondfrequency region, wherein a ratio between said first resonant frequencyand said highest frequency of the second frequency region may be largerthan 1.0, 1.1, 1.2, 1.4, 1.6, 1.8, or 2.0. In some other embodiments,said first resonant frequency is within the second frequency region. Insome other examples, said first resonant frequency is above the highestfrequency of the first frequency region and below the lowest frequencyof the second frequency region.

In the context of this document, a resonant frequency associated to aninternal port of the radiating structure preferably refers to afrequency at which the input impedance of the radiating structure, theimpedance being measured at said internal port, when disconnected fromthe radiofrequency system, has an imaginary part equal, or substantiallyequal, to zero.

A radiofrequency system according to the invention comprises two or morematching circuits with one, two, three, four, or more stages each, witheach stage comprising one or more circuit components (such as forexample, but not limited to, inductors, capacitors, resistors, jumpers,short-circuits, transmission lines, or other reactive or resistivecomponents). A stage can be connected in series or in parallel to otherstages and/or to one of the at least one port of the radiofrequencysystem. In some examples, the matching networks may alternate stagesconnected in series (i.e., cascaded) with stages connected in parallel(i.e., shunted), forming a ladder structure, or an L-shaped structure(i.e., series-parallel or parallel-series), or a pi-shaped structure(i.e., parallel-series-parallel) or a T-shaped structure (i.e.,series-parallel-series). A stage may also substantially behave as aresonant circuit (such as, for instance, a parallel LC resonant circuitor a series LC resonant circuit) in at least one frequency region ofoperation of the radiating system (such as for instance in the first orsecond frequency region).

Some or all of the matching networks advantageously comprise, in atleast one of their stages, a transmission line as set forth in thepresent invention. By means of said transmission line and, in someembodiments, together with other stages from said matching networks, afiltering effect may be provided to each signal path between oneradiation booster and the combining structure.

According to the present invention, some preferred matching circuitscomprise three, four, five or six components.

As such, an advantageous aspect of radiofrequency systems according thepresent invention is their efficiency in that impedance matching in thefirst and second frequency regions may be provided with matchingnetworks comprising reduced numbers of components, which consequentlyintroduces lower losses in the radiofrequency system and makes it morerobust against the tolerances of the components.

Particularly, the use of transmission lines configured to substantiallyblock electromagnetic wave signals of part or the totality of thefrequencies from the first or second frequency region further improvesindependence in the design of the first matching network from the secondmatching network. The characteristic impedances Z0 of the transmissionlines used in the matching networks as disclosed in the presentinvention are usually greater than 50Ω. The impedance varies based onthe width of the transmission line and the gap separating said line fromthe ground plane layer. Given particular width and gap values for thetransmission lines of a radiofrequency system, the correct adjustment ofthe lengths of the transmission lines may effectively block signals fromone or the other frequency region, in addition to other components fromthe matching networks that may contribute to blocking said signals too.

A radiofrequency system according to the present invention comprisesfirst and second matching networks, wherein each matching networkcomprises a transmission line with a total width (i.e., sum of the widthand the gap dimensions) that is equal or less than 4mm, preferably lessthan 3 mm, and more preferably substantially equal to 2 mm.

For those embodiments in which the total width of each of thetransmission lines is substantially 2 mm, it is considered that 1.5mm-wide lines separated 0.5 mm from the ground plane layer set aconvenient trade-off between the characteristic impedance and thetolerances of standard PCB manufacturing techniques for mass production.The lengths of the lines have to be adjusted properly, yet certaindeviations from the nominal width and gap values are expected due tofabrication inaccuracies, with the performance of the radiating systemhaving to be kept more or less similar. Such pair of values may bedifferent in other embodiments, wherein similar or different totalwidths of the transmission lines and with the lengths of the lines beingmodified accordingly.

A further aspect of the present invention relates to a test platform forelectromagnetically characterizing booster elements. Said platformcomprises a substantially square conductive surface on top of which, andsubstantially close to the central point, the element to becharacterized is mounted perpendicular to said surface in a monopoleconfiguration, said conductive surface acting as the ground plane.

The substantially square conductive surface comprises sides with adimension larger than a reference operating wavelength. In the contextof the present invention, said reference operating wavelength is thefree-space wavelength equivalent to a frequency of 900 MHz. Asubstantially square conductive surface according to the presentinvention is made of cupper with sides measuring 60 centimeters, and athickness of 0.5 millimeters.

In the test configuration as set forth above, a booster elementaccording to the present invention is characterized by a ratio betweenthe first resonance frequency and the reference frequency (900 MHz)being larger than a minimum ratio of 3.0. In some cases, said ratio maybe even larger than a minimum ratio such as: 3.4, 3.8, 4.0, 4.2, 4.4,4.6, 4.8, 5.0, 5.2, 5.4, 5.6, 5.8, 6.0, 6.2, 6.6 or 7.0.

A booster element according to the present invention may also becharacterized by a radiation efficiency measured in said platform, at afrequency equal to 900 MHz, being less than 50%, preferably being lessthan 40%, 30%, 20%, or 10%, and in some cases being less than 7.5%, 5%,or 2.5%. All those are quite remarkably low efficiency valuesconsidering the additional 1:3 frequency mismatch and beyond obtained insome of the embodiments as described above. Such a frequency shift wouldintroduce further mismatch losses that would result in an overallantenna efficiency below 5%, and quite typically below 2%, which wouldbe ordinarily considered unacceptable for a mobile phone or wirelessapplication. Still, quite surprisingly, when combining one or more ofsuch a low efficiency booster elements with the radiofrequency systemwithin the radiating system of a wireless device according to thepresent invention, said radiating system recovers the efficiencyrequired for the performance of a typical wireless device.

In some embodiments, a radiation booster according to the presentinvention may also be characterized with said platform comprising thesubstantially square conductive surface. In these embodiments, aradiation booster may feature a ratio between the first resonancefrequency and the reference frequency is larger than one, some or all ofthe aforementioned minimum ratios. Moreover, a radiation booster in somecases may also be characterized by a radiation efficiency measured insaid platform, at a frequency equal to 900 MHz, being less than 50%,preferably being less than 40%, 30%, 20%, or 10%, and even morepreferably being less than 7.5%, 5%, or 2.5%.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the invention will becomeapparent in view of the detailed description which follows of somepreferred embodiments of the invention given for purposes ofillustration only and in no way meant as a definition of the limits ofthe invention, made with reference to the accompanying drawings.

FIG. 1 shows a wireless handheld device, in an exploded view, comprisingan exemplary radiating system.

FIG. 2 shows schematically a radiating system according to the presentinvention.

FIG. 3A and FIG. 3B show exemplary radiating systems with diagrammaticrepresentations of radiofrequency systems.

FIG. 4A and FIG. 4B schematically show examples of matching networks fora radiofrequency system according to the present invention. Moreparticularly, FIG. 4A shows an exemplary matching network comprising atransmission line; and FIG. 4B shows an exemplary matching networksuitable for interconnection between the combining structure and theexternal port of a radiating system.

FIG. 5 shows, in a block diagram fashion, an example of a radiofrequencysystem according to the present invention.

FIG. 6 shows a possible reflection coefficient measured at the externalport of a radiating system which may be included in a wireless devicesuch as FIG. 1.

FIG. 7 shows a table with several transmission line gap and width ratiosand the associated characteristic impedances.

FIG. 8A and FIG. 8B show exemplary booster elements according to thepresent invention.

FIG. 9A and FIG. 9B show a test platform for the electromagneticcharacterization of booster elements.

FIG. 10 shows the radiation efficiency and antenna efficiency of abooster element according to the present invention measured with thetest platform depicted in FIGS. 9A-9B.

DETAILED DESCRIPTION

In FIG. 1 there is shown a mobile phone in an exploded view, the phoneincluding parts 101, 102, and 103. The mobile phone comprises anexemplary radiating system according to the present invention. Theradiating system comprises a radiating structure included in the printedcircuit board 102 comprising first radiation booster 104, secondradiation booster 105, and ground plane layer 106. The radiating systemfurther comprises the external port 107, and a radiofrequency systemwhich, for clarity, is shown with no components in the matching networksother than first transmission line 108, second transmission line 109,and a combining structure taking the form of conductive pad 110. Anexample of a complete radiofrequency system is shown in FIG. 5.

Although the device from FIG. 1 is a mobile phone, other wirelesshandheld or portable devices may include a similar radiating system.

A radiating system according to the present invention is shownschematically in FIG. 2. Said radiating system comprises the radiatingstructure 201, the radiofrequency system 202, and the external port 203.The radiating structure includes the first radiation booster 204 with aconnection point 205, the second radiation booster 206 with a connectionpoint 207, and a ground plane 208 with connection points 209 and 211. Afirst internal port 210 is defined between the connection point 205 ofradiation booster 204 and the connection point 209 of the ground plane208, and a second internal port 212 is defined between the connectionpoint 207 of radiation booster 206 and the connection point 211 of theground plane 209. The first radiation booster is connected to a firstfeeding line through connection point 205, and the second radiationbooster is connected to a second feeding line through connection point207. The radiofrequency system 202 is connected to said first and secondfeeding lines through connection points 213 and 214 of the feedinglines, and is also connected to the external port 203. Theradiofrequency system provides impedance matching to the radiatingstructure 201 at the external port 203 so that the radiating system isconfigured to operate electromagnetic wave signals from first and secondfrequency regions of the electromagnetic spectrum.

The ground plane 208 may be, for instance, a layer of a printed circuitboard acting precisely as a ground plane. It may also be formed in morethan one layer of a printed circuit board, with several layers beingelectrically connected; or even be formed in more than one printedcircuit board, with the ground plane layers being interconnected.

A radiating system with a schematic radiofrequency system 301 is shownin FIG. 3A. The printed circuit board 302 includes a radiating structurecomprising first radiation booster 303 which includes connection point321 in electrical contact with first feeding line 304 in the form of aconductive trace, second radiation booster 305 which includes connectionpoint 322 in electrical contact with second feeding line 306 in the formof a conductive trace, and a ground plane layer 307 comprising one ormore connection points.

The radiofrequency system 301 comprises first matching network 310,second matching network 311, third matching network 312 (matchingnetworks 310, 311 and 312 are shown empty for illustrative purposesonly) and combining structure 313 which in this particular example isformed as a conductive pad on the printed circuit board 302. The firstmatching network is defined between point 314 in the first conductivetrace 304 and the combining structure 313, the second matching networkis defined between point 316 in the second conductive trace 306 and thecombining structure 313, and the third matching network is definedbetween the combining structure and conductive pad 320. In this example,the external port 319 of the radiating system is defined betweenconductive pad 320 and the ground plane layer 307. Generally, thematching networks 310, 311, 312 may also be connected to the groundplane 307.

In FIG. 3A there are also shown the width 323 and gap 324 dimensionscharacterizing radiation booster 303, wherein gap 324 represents theminimum distance of an edge of the conductive part of the radiationbooster connected to the conductive trace 304 to the ground plane layer307, and wherein width 323, in the context of this invention, is takenas the smallest dimension of the radiation booster's footprint on theprinted circuit board 302. The ratio between width 323 and gap 324defines the location factor of the radiation booster. The locationfactor is preferably greater than 0.3, and/or 0.5, and/or 1.0, and ispreferably smaller than 3.5, and/or 3.0, and/or 2.5, and/or 2.0.

In FIG. 3A, the matching networks 310, 311, 312 do not include anycomponent for illustrative purposes only. An example of a suitablematching network for any of the first and second matching networks 310,311 is shown in FIG. 4A, and an example of a matching network that maybe added as the third matching network 312 is depicted in FIG. 4B.

It is readily apparent to the person skilled in the art that radiationboosters 303 and 305 may comprise a booster element like in the form ofbooster elements 800 and 810 of FIGS. 8A and 8B, or take any other formincluding the combination of more than one booster element. Thereforethe radiation boosters are not limited to the form of polygons 303 and305 (drawn with dashed lines) of FIG. 3A.

FIG. 3B also shows a radiating system wherein the radiating structurecomprises first radiation booster 351 formed by two booster elements,said radiation booster fits in an imaginary sphere having a diametersmaller than ⅓ of a radiansphere corresponding to the lowest frequencyof the first frequency region of the radiating system. The radiationbooster 351 is connected to conductive trace 352. The radiatingstructure further comprises second radiation booster 353 formed by onebooster element, and it is connected to conductive trace 354 of theprinted circuit board 302. Conductive traces 352 and 354 advantageouslyseparate radiation boosters 351 and 353, respectively, from the groundplane layer 355; said separation may improve the performance of theradiation boosters in terms of impedance bandwidth, and/or efficiency,and/or reflection coefficient. In preferred embodiments, the locationfactor of radiation boosters is at least 0.3 and less than 3.5, whereinsaid location factor is defined as the ratio between the width of theradiation booster and the separation between the radiation booster andthe ground plane layer.

In the context of the present invention, a first matching network isdefined between point 356 in trace 352 and a point in the combiningstructure 313, a second matching network is defined between point 357 intrace 354 and a point in the combining structure 313, and a thirdmatching network is defined between a point in the combining structure313 and a point in pad 320, wherein said pad 320 may further define theexternal port 319 of the radiating system as shown in FIG. 3A. In somecases, a bandwidth target may be achieved at the combining structure andthe third matching network may not be necessary, in which case it isalso possible that the external port of the radiating system may bedefined between the combining structure 313 and the ground plane layer355.

The first matching network, in addition to other components not drawn inFIG. 3B but shown in FIG. 4A and FIG. 5, comprises a first transmissionline 358 characterized by width 360, gap or separation 361 from theground plane layer 355, and a length. The second matching network, whichalso comprises other components not represented in FIG. 3B but shown inFIG. 4A and FIG. 5, includes a second transmission line 359 that is alsocharacterized by a width, a gap from the ground plane layer 355, and alength. In this embodiment, both transmission lines 358 and 359 featurethe same width 360 and gap 361. The correct election of the lengths ofthe transmission lines, depending on the given width 360 and gap 361values, and together with the rest of the components from the respectivematching networks, makes the impedance measured at the combiningstructure 313 towards the first radiation booster 351 to be particularlyhigh for some or all frequencies of the one frequency region (e.g., thesecond frequency region), and the impedance measured at the combiningstructure 313 towards the second radiation booster 351 to beparticularly high for some or all frequencies of the other frequencyregion (e.g., the first frequency region). The first and second matchingnetworks also provide impedance matching to frequencies for which theinput impedance at the combining structure is not high, namely thefrequencies from the other one of the first and second frequencyregions. In those cases in which said impedance matching does notachieve a bandwidth target in one or both frequency regions, the thirdmatching network further tunes the impedance for the combinedelectromagnetic wave signals so as to achieve said bandwidth target;conductive pad 362 may be convenient for allocating part of said thirdmatching network. A circuit that may be suitable for the third matchingnetwork may be seen in FIG. 4B and FIG. 5.

A particularity of transmission lines 358 and 359 is that there is noground plane near the edge of the transmission lines that is closer toradiation boosters 351 and 353, and ground plane is mainly present atthe opposite side (the side defining gap 361). Generally, almost noground plane is present at one side of the transmission lines. In lesspreferred embodiments, there may be a ground plane layer substantiallybeneath the transmission lines, such as a layer of a multilayer printedcircuit board that may be below said lines. In addition, and even thoughthe lengths of transmission lines 358 and 359 in FIG. 3B issubstantially similar, in other embodiments the length of the firsttransmission line may be different to the length of the secondtransmission line.

A matching circuit as represented in FIG. 4A may be used in any of thefirst and second matching networks of a radiofrequency system accordingto the present invention. Although a particular topology is shown, othertopologies may also be used as long as one of the components in thematching network is a transmission line as disclosed in the presentinvention. In this particular example, point 401 is to be connected to afeeding line such as 352 or 354 in FIG. 3B (corresponding either topoint 356 or 357 for example), and point 402 is to be connected to thecombining structure like 313 in FIG. 3A or FIG. 3B. In this particularcase, the matching circuit comprises four stages: the first stageincludes series component 404, the second stage includes two shuntedcomponents 405 and 406 which are connected to a ground plane 403, thethird stage comprises transmission line 407, and the fourth stagecomprises component 408 connected in series between transmission line407 and point 402. In other embodiments, such a matching circuit maycomprise less than four stages or more than four stages.

The matching network is advantageously configured so that the inputimpedance measured at port 409 is high for part or the totality of thefrequencies comprised in one of the first and second frequency regions,thus substantially blocking electromagnetic wave signals from saidfrequency region, whereas impedance matching at port 409 is partial ortotal for the other one of said first and second frequency regions.

Regarding FIG. 4B, an exemplary matching circuit suitable for the thirdmatching network of a radiofrequency system is depicted. In thisparticular circuit, point 411 is connected to the combining structuresuch as 313 in FIG. 3A or FIG. 3B, and point 412 connects to a pad (suchas 320 in FIG. 3A or FIG. 3B) that also defines the external port of theradiating system. The matching circuit comprises three stages, but inother examples it may comprise one, two, or more than three stages. Thefirst stage corresponds to component 413 in series, the component 414from the second stage is in parallel and connected to ground plane 403,and third stage comprises component 415 also in series. The inputimpedance or the reflection coefficient achieves a bandwidth target whenmeasured at port 416.

All the circuit components from FIGS. 4A-4B other than the transmissionlines may be any of the following, but not limited to: inductors,capacitors, resistors, jumpers, short-circuits, transmission lines, orother reactive or resistive components. The combination of componentsand topologies of the matching networks depend on the particularcharacteristics of the radiating system like, for example: the frequencyregions of operation of the radiating system; the radiation boostersused and their location in the wireless device; the lengths and shapesof the conductive traces; the dimensions and shapes of the ground planelayers; the width, length and gap parameters of the transmission lines;the electronics and circuitry of the device that are nearby theradiating structure, etc.

FIG. 5 depicts an illustrative example of a radiofrequency system withthe first matching network being defined between points 501 (in a firstfeeding line that connects to a first radiation booster), 502 (in thecombining structure), and 503 (in the ground plane); the second matchingnetwork being defined between points 504 (in a second feeding line thatconnects to a second radiation booster), 505 (in the combiningstructure), and 506 (in the ground plane); and the third matchingnetwork being defined between points 507 (in the combining structure),508 (in a conductive pad that may further define the external port ofthe radiating system), and 509 (in the ground plane).

Although in this specific embodiment particular matching networktopologies and component combinations are represented, it will bereadily apparent to the person skilled in the art that other matchingnetworks are also possible according to the teachings of the presentinvention.

FIG. 6 is a graph representing an exemplary reflection coefficientversus frequency measured at the external port of a radiating systemaccording to the present invention. In this particular graph, thereflection coefficient 601 is equal or lower than −6 dB in the firstfrequency region 602 ranging from 698 MHz to 960 MHz, and in the secondfrequency region 603 ranging from 1710 MHz to 2690 MHz. Such performancemay be achieved, for example, by the radiating system from FIG. 3Bincluding the radiofrequency system from FIG. 5.

In other embodiments, the reflection coefficient target may be evenlower or greater like for instance −4.4 dB; and/or the first and secondfrequency regions may comprise ranges of frequencies different from theones shown in FIG. 6.

A table showing pairs of width and gap values of transmission lines isrepresented in FIG. 7. Specifically, the characteristic impedance (Z0)is indicated for few width-gap pairs when the total width of thetransmission line is 2 mm, 3 mm, and 4 mm when no ground plane layer islocated beneath the transmission line, although the invention is notlimited by the presence or absence of ground plane below thetransmission lines.

As represented in the table, the characteristic impedance decreases asthe gap is reduced. Accordingly, for given width and gap values thatpreferably make the transmission line to have a characteristic impedancebetween 75Ω and 150Ω, the length of the transmission lines has to be setproperly to make the radiating system operable in first and secondfrequency regions. And for the radiating system to support thetolerances in the PCB manufacturing process, gaps of about 0.5 mm areconvenient as slight variations in the fabrication do not have an impactas large as in the case of gaps of 0.2 mm or even 0.1 mm. So for apreferred embodiment with transmission lines featuring a total width of2 mm, a width of 1.5 mm and a gap of 0.5 mm advantageously make theradiating system operable in two frequency regions by adjusting thelengths of the lines.

Two exemplary booster elements are shown in FIG. 8A and FIG. 8B. Thebooster element 800 comprises a first conductive surface 801, a secondconductive surface 802, a dielectric element or support 803 (showntransparent for illustrative purposes only), and several via holes 804electrically connecting the first conductive surface 801 with the secondconductive surface 802. The first and second conductive surfaces 801 and802 substantially feature rectangular shapes.

The booster element 810 from FIG. 8B comprises a first conductivesurface 811 and a second conductive surface 812, each of which aresubstantially shaped as squares, although other shapes are possible aswell. Said surfaces 811 and 812 are electrically connected by via holes814 going through the dielectric material 813.

Both booster elements 800 and 810 may be configured to function as aradiation booster in every radiating structure according to the presentinvention in a single configuration as radiation booster 353 of FIG. 3B,or in a multiple configuration like 351 in FIG. 3B wherein two or morebooster elements are connected yet they are configured to function as asingle radiation booster.

A connection point (such as 205 and 207 in FIGS. 2; or 321 and 322 inFIG. 3A) of booster elements such as 800 and 810 may be locatedsubstantially close to one corner of one of the first and secondconductive surfaces.

FIG. 9A schematically shows, in a 3D perspective, a test platform forthe characterization of booster elements. The platform comprisessubstantially square conductive surface 901 and connector 902 (forinstance an SMA connector) electrically connected to the device orelement 900 to be characterized. The conductive surface 901 has sideswith a length larger than the reference operating wavelengthcorresponding to the reference frequency. For instance, at 900 MHz, saidsides are at least 60 centimeters long. The conductive surface may be asheet or plate made of cupper, for example. The connector 902 is placedsubstantially in the center of conductive surface 901.

In FIG. 9B the same test platform of FIG. 9A is schematicallyrepresented in a 2D perspective wherein the conductive surface 901 ispartially drawn. In this example, the element that is to becharacterized 900 in FIG. 9A corresponds to booster element 800 fromFIG. 8A, which is arranged so that its largest dimension isperpendicular to conductive surface 901, and one of the first or secondconductive surfaces (801 or 802 of FIG. 8A) is in direct electricalcontact with connector 902 (for clearer interpretation of theorientation of booster element 800, via holes 804 connecting the firstand second conductive surfaces of booster element are also drawn in FIG.9B). The booster element 800 lies on a dielectric material (not shown)attached to the conductive surface 901 so as to minimize the distancebetween booster element 800 and surface 901. Said dielectric materialmay be a dielectric tape or coating, for example.

FIG. 10 shows an graph of the radiation efficiency and antennaefficiency measured in a test platform like the one shown in FIG. 9A andFIG. 9B, when the element 900 to be characterized is booster element800. In this particular example, the radiation efficiency measured 1001(represented with a solid line) at 900 MHz is less than 5%, and theantenna efficiency measured 1002 (represented with a dashed line) at 900MHz is less than 1%.

The foregoing is merely illustrative of the principles of this inventionand various modifications can be made by those skilled in the artwithout departing from the scope and spirit of the invention.

What is claimed is:
 1. A wireless device comprising a radiating systemconfigured to operate electromagnetic wave signals from a firstfrequency region and a second frequency region, the radiating systemcomprising: a radiating structure, a radiofrequency system, and anexternal port; the radiating structure comprising: a ground plane layer;and a first radiation booster connected to a first feeding line, asecond radiation booster connected to a second feeding line, whereineach of the first and second radiation boosters fits in an imaginarysphere having a diameter smaller than ⅓ of a radiansphere having aradius equal to a free-space wavelength corresponding to a lowestfrequency of the first frequency region, divided by two times π; theradiofrequency system comprising: a combining structure; a firstmatching circuit including a first transmission line; a second matchingcircuit including a second transmission line; and a third matchingcircuit; wherein the first matching circuit is connected to the firstfeeding line and the combining structure, the second matching circuit isconnected to the second feeding line and the combining structure, andthe third matching circuit is connected to the combining structure andthe external port; wherein the radiofrequency system modifies impedanceof the radiating structure to provide impedance matching to theradiating system within the first and second frequency regions at theexternal port; wherein each of the first and second transmission linesis characterized by a width dimension equal or greater than 1 mm, andless than 3.5 mm; and wherein a minimum distance of each of the firstand second transmission lines to the ground plane layer is greater than0.1 mm, and equal to or less than 1.0 mm.
 2. The wireless deviceaccording to claim 1, wherein a highest frequency of the first frequencyregion is lower than a lowest frequency of the second frequency region.3. The wireless device according to claim 2, wherein the first frequencyregion comprises an 824-960 MHz frequency range, and the secondfrequency region comprises a 1.71-2.69 GHz frequency range.
 4. Thewireless device according to claim 2, wherein the first frequency regioncomprises a 698-960 MHz frequency range, and the second frequency regioncomprises a 1.71-2.69 GHz frequency range.
 5. The wireless deviceaccording to claim 1, wherein: an input impedance of the radiatingstructure measured at a connection point between the first radiationbooster and the first feeding line, when the radiating structure isdisconnected from the radiofrequency system, has an imaginary part notequal to zero for any frequency of the first frequency region; and aninput impedance of the radiating structure measured at a connectionpoint between the second radiation booster and the second feeding line,when the radiating structure is disconnected from the radiofrequencysystem, has an imaginary part not equal to zero for any frequency of thefirst frequency region.
 6. The wireless device according to claim 5,wherein: the input impedance of the radiating structure measured at theconnection point between the first radiation booster and the firstfeeding line, when the radiating structure is disconnected from theradiofrequency system, has an imaginary part not equal to zero for anyfrequency of the second frequency region; and the input impedance of theradiating structure measured at the connection point between the secondradiation booster and the second feeding line, when the radiatingstructure is disconnected from the radiofrequency system, has animaginary part not equal to zero for any frequency of the secondfrequency region.
 7. The wireless device according to claim 1, whereinthe first radiation booster comprises two booster elements, and thesecond radiation booster comprises one radiation booster.
 8. Thewireless device according to claim 7, wherein each of the two boosterelements of the first radiation booster and the one booster element ofthe second radiation booster features a ratio between a first resonancefrequency and a reference frequency of 900 MHz is larger than 3.0 whenmeasured in a monopole configuration in a platform comprising asubstantially square conductive surface made of cupper, the platformcomprising sides of 60 centimeters and a thickness of 0.5 millimeters.9. The wireless device according to claim 8, wherein each of the twobooster elements of the first radiation booster and the one boosterelement of the second radiation booster features a radiation efficiencythat is less than 10%, at a frequency equal to 900 MHz, when measured ina monopole configuration in a platform comprising a substantially squareconductive surface made of cupper, the platform comprising sides of 60centimeters and a thickness of 0.5 millimeters.
 10. The wireless deviceaccording to claim 1, wherein an input impedance of the radiatingstructure, measured at the combining structure, of a first signal pathdefined between the first radiation booster and a connection pointbetween the first matching network and the combining structure isgreater than 200Ω for some or all frequencies of the second frequencyregion.
 11. The wireless device according to claim 10, wherein an inputimpedance of the radiating structure, measured at the combiningstructure, of a second signal path defined between the second radiationbooster and a connection point between the second matching network andthe combining structure is greater than 200Ω for some or all frequenciesof the first frequency region.
 12. The wireless device according toclaim 1, wherein: each of the first and second transmission lines ischaracterized by a width dimension substantially equal to 1.5 mm; andthe minimum distance of each of the first and second transmission linesto the ground plane layer is substantially equal to 0.5 mm.